In vehicles, transmissions connect between internal combustion engines and driving wheels. The transmission controls the driving force of driving wheels and the driving speed, depending on a driving condition varying extensively, and thus sufficiently optimizes the performance of an internal combustion engine. Among a variety of transmissions, there is a belt driving type of non-stage automatic transmission. This type of transmission serves to change, by hydraulic pressure, the groove widths formed between respective driving and driven adjustable pulleys. Thus, by varying the radius of a belt wound around the driving and driven pulleys, the reduction ration (belt ratio) relative to a driving force transmitted by the belt may be changed.
This type of non-stage automatic transmission for a vehicle is disclosed in Japanese Patent No. 59-126145. In the control device of the transmission disclosed in this patent, the reduction ratio of the control mechanism is controlled at the up-shift side when the number of revolutions increases higher than a predetermined number, and the reduction ratio is controlled on the down-shift side when the number of revolutions decreases lower than a predetermined number of revolutions. Thus, in the transmission, an acceleration feeling is caused from increasing the number of engine revolutions and the response to increasing torque in pushing down an accelerator pedal is improved, and hunting is prevented by the speed control.
A further problem in the existing non-stage transmissions is that the torque convertor, the oil pump, the driving pulley, the clutch, and the brake are positioned in a row from the engine side along a driving side shaft of the transmission. It is difficult and practically disadvantageous to arrange such a transmission in the limited engine space, because the overall length is large. In addition, the belt-pulley arrangement requires a multi-shaft structure which, because of the layout of bearings which support multiple shafts, structure is complicated and inevitably leads to high costs and economic disadvantages.
Accordingly, an object of the present invention is to provide a non-stage automatic transmission which can be composed in smaller size and easily arranged in the engine space or room. This object is addressed by positioning in turn a fluid coupling having normal and reverse rotating functions, an oil pump producing a driving hydraulic pressure, a reverse driving brake, a forward-reverse shift clutch, and an adjustable driving pulley in a row from engine side along the driving rotation shaft of the transmission.
Another non-stage transmission is disclosed in Japanese Patent No. 59-99165. In a hydraulic pressure controlling device of the non-stage automatic transmission for a vehicle which was disclosed in this patent, an input shaft of a belt type of non-stage automatic transmission is an output shaft, and on the output shaft, a non-stage automatic transmission, a planetary gear for shifting advance and reverse, an oil pump, and a three-element one-stage type of torque convertor are in turn positioned from the engine side.
Also, in Japanese Patent No. 58-121349, this type of transmission is disclosed. In a hydraulic pressure controlling device of the non-stage automatic transmission disclosed in this patent, on an output shaft of an engine, a three-element one-stage type of torque converter, a driving pulley, and an oil pump are in turn positioned from the engine side, and on a shaft of a driven pulley, a multi-plate clutch for shifting advance and reverse, and a driving gear for advance and reverse are laid in order.
Also in the existing non-stage transmission for a vehicle, a torque convertor (a fluid coupling of PTS type in which a pump impeller, turbine runner, and a stator are in turn positioned, or of PST type in which a pump impeller, a stator and a turbine runner are in turn positioned) is used, and the stator of the torque convertor is either locked or freely rotatable, whereby it serves to operate as a reverse rotation torque convertor or a normal rotation fluid coupling, respectively.
However, since a brake and a direct clutch usually do not interlock together, a fluid coupling, for example, a torque convertor is in a condition which they are apt to slip with respect to each other, and a problem of reduced efficiency of driving power arises.
Besides, locating a direct clutch, as used for reversing, outside a torque convertor, for example, on the end or side opposite to the input side of an input shaft, makes large the overall length of a non-stage transmission. Therefore it is difficult to arrange the transmission in the limited space of the engine room due to this enlarged size.
Then, another object of the invention is, in order to improve the above-mentioned problem, to provide a non-stage transmission with a fluid coupling having a pump impeller, a stator to be locked by a brake, and a turbine runner in turn positioned and installed therein, and having a built-in direct clutch so as to prevent cavitation Thus, secure prevention of cavitation allows transmission efficiency of driving-power to be improved and, moreover, ensures a function as a damper by slipping of the direct clutch.
By comprising components as described above, when locking the stator with the brake, cavitation can be prevented to improve transmission efficiency of driving-power by engaging the direct clutch in the fluid coupling in interlocking with the brake, and the size of the non-stage transmission can be minimized. Moreover, a function of a damper can be ensured.
It was also devised to install a fluid coupling for shifting a direction of rotation of the belt to advance or reverse the vehicle. The fluid coupling has a pump impeller rotatably connected with the internal combustion engine, a rotating stator which can be locked by a braking mechanism, and a turbine fixed on an output side shaft which is in turn positioned on the pulley side. By releasing or locking the stator, the turbine rotates normally or reversely to shift the direction of rotation of the belt, and thus advance or reverse the vehicle.
However, in the known non-stage transmission equipped with a fluid coupling having a braking mechanism releasing and locking the stator to shift the direction of rotation of the turbine in the fluid coupling, a working mechanism operates the braking mechanism, and other components are in turn positioned in a row so that the overall length is large and requires a long space for accommodating these components. This makes it difficult to arrange the transmission in the limited engine room. Thus, this enlargement of the transmission is practically disadvantageous.
Therefore, a further object of the invention is to design a minimally-sized non-stage transmission equipped with a fluid coupling and which can be easily arranged in an engine room. This object is addressed by installing a braking operator of a working mechanism which operates a braking mechanism in a hollow portion formed inside of a retaining portion of a brake side casing, which casing also holds a bearing supporting an output side shaft of the fluid coupling. Such a construction makes it unnecessary to arrange a braking operator together with other components in a row in a non-stage transmission, so the non-stage transmission equipped with a fluid coupling can be made smaller in overall length and can be designed to a minimum size and length. Thus, the smaller non-stage transmission has the advantage of arrangement.
A further problem in traditional non-stage automatic transmissions is that the transmission case in which the mechanisms are supported has many components and therefore access to the mechanisms in the transmission case is difficult. That is, in traditional non-stage automatic transmission 200, for example as shown in FIG. 15, a transmission case 202 comprises a main case 204, a front case 206 fitted between the main case 204 and internal combustion engine (not shown), a rear case 208 fitted on the side of the main case 204 opposite the internal combustion engine, a subcase 210 fixed in said main case 204, and a rear cover case 212 fitted on the side of the main case 204 opposite the internal combustion engine. A belt type transmission mechanism 214 is installed and enclosed by the rear case 208 and the rear cover 212. A driving side shaft 216 and a driven side shaft 218--or rotation shafts--are each supported at one axial end by said front case 206, and at the other axial end by the main case 204 respectively. Also, a transfer gear 222 and a differential gear 224 composing a driving-power transmitting mechanism 220 are installed and enclosed by said front case 206 and said subcase 210 fixed in said main case 204. A transfer gear shaft 226--or a rotation shaft of the transfer gear 222--is supported at one axial end by said front case 204, and at the other axial end by said subcase 210. A differential gear case 228--a rotation shaft of the differential gear 224--has one axial end supported by the front case 206, and another axial end supported by said main case 204.
Meanwhile, as shown in FIG. 16, another known transmission case 302 of a non-stage automatic transmission 300 comprises a main case 304, a front case 306 fitted on the side of the main case 304 close to an internal combustion engine (not shown), a rear case 308 fitted on the side of the main case 304 opposite the internal combustion engine, a subcase 310 fixed on said main case 304, a front cover case 312 fitted on the side of the front case 306 close to the internal combustion engine, and a rear cover case 314 on the side of the rear case 308 opposite the internal combustion engine. A belt type transmission mechanism is installed and enclosed by said main case 304, said front case 306, said rear case 308, and said subcase 310. A driving side shaft 318 and a driven side shaft 320 have respective axial ends supported by said main case 304 and said front case 306, and respective opposite axial ends supported by said rear case 308 and said subcase 310. Also, a transfer gear 324 and a differential gear 326 composing a driving-power transmitting mechanism are installed and enclosed by said front case 306, said front cover case 312, and said main case 304. Transfer gear shaft 328--a rotation shaft of a transfer gear 324--has one axial end supported by said front case 306, and another axial end supported by said main case 304. A differential gear case 330--a rotation shaft of the differential gear 326--has one axial end supported by said front case 306, and another axial end supported by said main case 304.
As described above, in the known non-stage automatic transmission 200 of FIG. 15, the transmission case 202 comprises the main case 204, the front case 206, the rear case 208, the subcase 210, and the rear cover 212. Thus, including an oil pan (not shown) fitted on the transmission case 202, the number of case members forming the transmission case 202 amounts to six. Also, in the non-stage automatic transmission for a vehicle 300 shown in FIG. 16, the transmission case 302 comprises the main case 304, the front case 306, the rear case 308, the subcase 310, the front cover 312, and the rear cover 314. Including an oil pan (not shown) fitted on the transmission case 302, the number of case members amounts to seven. Accordingly, the traditional non-stage automatic transmission has the disadvantage of a large number of case members which is accompanied by rising costs, and carrying out maintenance is not easy because of difficult access to the mechanisms in the transmission case.
Thus, another object of the invention is to provide a non-stage automatic transmission for a vehicle in which the number of components composing the transmission case can be reduced, and in which each mechanism in the transmission case is simply accessible to easily carry out maintenance. This object is addressed by providing a transmission case which comprises a main case, and front and rear cases respectively fitted on the main case, such that one axial end of each rotation shaft of said mechanism is supported, enclosed, and installed by the main case, and another axial end of each rotation shaft of each mechanism is supported, enclosed, and installed by either said front case or said rear case. Thus, the construction has at least two less case elements than the known cases, and each mechanism will be easily accessible by removing either the front case the rear case.